It's here that the 'quirk' comes into its own!
The quirk is often and interchangeably called a 'fillet' by architects etc., referring to the blank, decorative strip above and below a moulding. However, for carvers the 2 words are differentiated: The quirk is any fillet run into the moulding itself and thus separates elements, such as the ends of leaves.
So... in our gadrooning, the original blank 'fillet' below the thick end of the moulding sneaks into the moulding itself to make the rounded ends, and thus becomes the quirk.
The ends of the gadroon can be a semicircle or flattened a little. It's up to you as the artist/carver!